OP 221Schultz, L.P., 1930. The life history of Lampetra planeri Bloch, with a statistical analysis of the rate of growth of the larvae from western Washington. 39 pp., 2 plates, 10 figures, 4 tables. $3.10

OP 230Hubbs, C.L., 1931. Studies of the fishes of the order Cyprinodontes, IX: A new and primitive genus of Poeciliidae from Central America. 3 pp., 1 figure. $0.50

OP 231Hubbs, C.L., 1931. Studies of the fishes of the order Cyprinodontes, X: Four nominal species of Fundulus placed in synonymy. 8 pp. $0.80